Voicepipes and Speaking-Tubes

Updated: 15 Mar 2010
US Navy info added

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There is a certain beauty of simplicity about the voicepipe concept. It is simply a pipe, and you talk (or shout) down it. The person at the far end cocks an ear to it then shouts back. At each end is a funnel-shaped horn, which probably matches the acoustic impedance of free air to the impedance of the pipe.

Voicepipes were used in affluent houses, (to demand tea from the maid) in expensive cars, (to talk to the chauffeur) and in early aeroplanes. (where wind & engine noise made normal speech between pilot and observer/gunner impossible) However their best-known application was on ships, and particularily warships.


Left: The picture shows a typical voicepipe installation in the Action Information Centre of HMCS Haida, the last remaining example of the 27 Tribal Class destroyers built from 1937 to 1945. The basic pipe diameter appears to be about 4 inches.

The voicepipes are covered with white lagging; this is probably to reduce acoustic interference. See below.

Above: a flexible termination to a voicepipe in the HFDF compartment of HMCS Haida. HFDF (huffduff) was a rapid direction-finding system that did U-boats no good at all, but that is another story.

Voicepipes have obvious advantages in naval warfare. They do not depend on electrical power, are immune to EMP, and will keep working after almost any amount of damage short of physical destruction. Such damage can of course occur, and was considered to be a contributory cause of the Russian defeat by the Japanese at the battle of Tsushima in May 1904.

There are snags of course; voicepipe communication between two water-tight compartments presents a clear risk of flooding, and requires shut-off valves to be fitted either side of the bulkhead, as you may not be able to get to one side of it...

Left: A voicepipe in the wheelhouse of the minehunter HMS Bronington.

This ship was completed in 1954 so voicepipes were clearly still current technology then. The pipe diameter seems to have increased over the WW2 version; or possibly the lagging is thicker.

Left: End fittings for voicepipes on the open deck.

The hinged covers keep out rain and spray. The location of the other end of the pipe is indicated on the brass plate in the middle of the flap.

Left: A voicepipe in one of the forward gun turrets of HMS Belfast.

HMS Belfast is a WW2 cruiser preserved and moored just above Tower Bridge, in London. The brass plate reads "Handing Room" which appears to be a misprint for "Handling room" ie the shell handling room below the gun turret. However, some correspondents have told me that "Handing Room" is in fact correct.

The pipe is of 2-inch diameter, and has no lagging on it.

Noted in the Scientific American Supplement for May 1897:

"A form of speaking tube for use of steamers has recently been introduced in England. The pecularity of it lies in the fact that the pipe is insulated from the body of the ship by a covering of waterproof textile material. This latter, being a very bad conductor of sound, enables long lengths of tube to be used without rendering the speech transmitted inaudible at the far end. The distance from the bridge to the engine room on the steamer India is over 300 feet, yet even with the engines running it is possible to hear clearly in the engine room, through the tube there fitted, orders given on the bridge. An electric call is fitted, as the ordinary whistle cannot be used for so long a length of pipe."

This appears to explain the white lagging on the voicepipes shown above; it was to reduce acoustic interference.

Left: Voicepipes in action. This is the compass platform of a British ship (probably a cruiser) in action during the Second World War.

Voicepipes with their covers open can be seen grouped around the compass, with its two large compensating spheres.

The man on the right holding the microphone is the Torpedo Officer, who is giving the ship's company a running commentary through the ship's PA system, which was of course electrical.

Everyone is wearing anti-flash gear in addition to their steel helmets.

My correspondent, known only as "Joe Schumckitelli" writes:

"I was in the US Navy for 4 years as in Interior Communications Electrician. The voice pipes fell under my responsibility for maintainence and repair (among other things). Conveniently, the voice pipes never needed either maintainence or repair, as they were never used because electronic communication devices were much more audible. Even during a power failure, sound powered telephones were used. The voice pipes were designated circuit "Y," or "CKT Y." All communications circuits, both electrical and non-electrical had circuit names."

This extract comes from the US Naval document "General Specifications- Appendix 10" (1936) which describes the Nomenclature of decks, Numbering of watertight compartments and Labeling on US vessels:

"Voice tube numbers shall be assigned serially in accordance with the voice tube list, each number bearing the prefix "VT" instead of the composite number above described. Each voice tube shall be labeled at least once in each compartment through which it passes, with a tag permanently secured to the tube in such a manner that the tube can be readily identified. At the outlets, labels shall be fitted both on the inside and outside of the cover, so that the tube number and the station to which the voice tube leads will be clearly shown at all times. Where such label plates may be installed close to and above the mouthpiece in such a manner that the voice tube can be readily identified whether open or shut, it will not be necessary to install labels on the cover proper."

It appears that some Japanese aeroplanes in WW2 were fitted with voicepipes for inter-crew communication; see www.historyplace.com (external link)


As a general rule "voicepipe" is a maritime term, and those on land were usually called "speaking-tubes". A normal installation had a removable whistle plugged into each end. To initiate a conversation Person A removed his whistle and blew down the tube, sounding the whistle at the other end. Person B then removed his whistle, and talking could begin. Hence the expression, still current in Britain, "I'll get him on the blower" when a telephone call is meant.
Such systems appear to have been quite common in homes and offices, though very little information about them, and very few references to them, seem to remain today.

I have secured one passage about speaking tubes from the memoirs of Sir Aylmer Firebrace, CBE, who was Chief of the Fire Service 1941-47:
"Internal house telephones were a long time coming in; speaking tubes were used instead. They were still in place- and some were in daily use- when I joined. The vicinity of the Chief Officer's desk literally bristled with speaking tubes, whilst the quarters provided for me, formerly the top two floors of Massey Shaw's house, had a voice pipe in every room, including bathrooms. They were in general use at fire stations; the modern expression "Give me a ring" was in those days, "Get me on the blower." The duty man (man on duty in the watch room) would gain the officer's attention by blowing up the tube to his quarters and so operating the removable whistle inserted in the end."

One of the very few firm statements on performance I have been able to find comes from "Manufacturer and Builder" for Mar 1872: "Two persons standing at each end of a simple tin pipe, 1 inch in diameter, 50 to 100 feet or more long, with several elbows in it, and carried through a half a dozen rooms, can still converse quite readily in a low voice."

Terrestrial speaking tubes had a smaller diameter than the sea-going version, with diameters from 15 to 25mm being quoted. This smaller diameter was easier to conceal in walls and under floors, but would given more volume loss. This was tolerable for short pipe runs in a relatively quiet environment. Shipboard voicepipes, in contrast, had longer pipe runs, and had to compete with the noise of machinery and weather; this is probably why they were larger in diameter.
The acoustic losses in a tube are due to viscous friction between the vibrating air and the walls of the tube. Thus a bigger tube gives lower losses, as on doubling the diameter, the wall area for a given length is also doubled, but the mass of air in that length is quadrupled.
In fact the loss in dB is inversely proportional to the area, and hence to the diameter squared. The theoretical attenuation of a 5-cm (2-inch) diameter voicepipe is 30 dB per 100 metres.

Left: An office in 1903. There are four flexible speaking-tubes hooked on the end of the table.

The elliptical funnel shape of the mouthpiece on each tube is presumably to make it easier to blow down the tube to activate the calling whistle at the far end.

Left: A cartoon featuring an automotive speaking-tube.

Images of car and aeroplane voicepipes have proved very hard to come by. The best I can do so far is this cartoon, published in Lilliput* for October 1946; the lady in the back is presumably supposed to be playing a trumpet solo on the voicepipe, to the displeasure of her chauffeur. Such devices were clearly not wholly obsolete then, as the cartoonist assumed his audience would know what he was depictng.

The horn at the driver's end is placed handily by his ear, but it is not obvious how he could reply without turning his head and taking his eyes off the road. Some sort of response was presumably expected, if only "Yus, m'lady"

* Lilliput was a pocket-sized magazine published during and after the Second World War in Britain.

I received this email from Mr Vincent Griffin on 11th April 2008, and I reproduce it here (with permission) as it gives some insight into domestic speaking tubes, and in the hope that someone may be able to answer his query. If so, please contact me.

My wife and I have a Victorian house that was built in 1895 and for the past two years we've been in the process of rehabbing it. During the course of demo in the kitchen we found the remnants of the old speaking tube system that ran from the kitchen up to the 2nd floor hall. The tubes were intact but the mouthpiece openings had been patched over and the mouthpieces were nowhere to be found. I have looked far and wide trying to locate some replacement mouthpieces and have come up empty-handed. We were wondering if you know of any companies and/or salvage yards that might possess parts for our system? Your help would be greatly appreciated. I've included a pic of what I believe was originally installed in my house. The mouth piece has no electric parts. It operates by means of using the thumb to rotate the lever (in order to move the disc out of the way) and then blowing into the tube. The other end also has a disc that acts as a whistle to alert the person on the other end that someone wishes to speak on the "intercom". I think that the mouthpieces were made out of nickel-plated brass and/or porcelain. I appreciate any help that you could give me. Vince Griffin

Left: The picture that Vincent Griffin sent.

The lever on top moves aside the disc containing the whistle to allow blowing or talking.

The mouthpieces could be ordered "with indicator". This is pure speculation, but I assume it was some sort of pressure operated flag that gave a persistent indication that a particular pipe had been blown. If you were sitting in the servant's hall faced with half-a-dozen speaking tubes connected to various parts of a large house, that could have been very useful.

Good grief, you can still buy these things! See diytools.co.uk (external link) for a speaking tube that communicates with visitors at the front door.

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